DE102017107627A1 - Bonding method and bonding device for a metal element - Google Patents

Abstract

A bonding method includes: an oxide film forming step S10 of forming on an irradiated surface 62a1 an oxide film OM having a film thickness corresponding to a first output W1 and an irradiation time of a laser beam L1 forming the oxide film; a step S12 for detecting a first reflected laser beam to detect a second output W2; a first absorptivity calculation step S14 of calculating a first absorptivity for the laser film L1 forming the oxide film; Laser beam switching steps S16A and S16B for switching the oxide film forming laser beam irradiated on the irradiated surface 62a1 to a hot bond laser beam; and a warm bonding step S3 of heating a first bonding surface 62b until the temperature thereof reaches a predetermined bonding temperature Ta and bonding the first bonding surface 62b to a second bonding surface 51a.

Description

BACKGROUND OF THE INVENTION

1. Field of the invention

The present invention relates to a bonding method and a bonding apparatus for a metal member using a laser beam.

2. Description of the Related Art

There is a known technology in which a metal member is heated by irradiating a laser beam onto a surface of the metal member and causing the metal member to absorb the laser beam. See Japanese Patent No. 4894528 ( JP 4894528 ), Japanese Patent No. 5602050 ( JP 5602050 ), and Japanese Patent Application Laid-Open No. 2014-228478 ( JP 2014-228478 A For example, in this there are different threads for heating a metal element. For example, one of these reasons is to bond two elements, as in the JP 4894528 and the JP 5602050 is described. For example, when two elements are bonded, a metal element (eg, a lead wire) serving as a contact of an electric circuit is heated, and a member to be bonded (eg, a semiconductor terminal) and the metal member are directly bonded together. In this case, as in the JP 4894528 and the JP 5602050 is described while keeping a heated portion in a solid phase without sufficiently heating the portion to change the state to a state of a liquid phase, the metal member and the member to be bonded are pressed against each other with a predetermined pressure to be bonded together to become (solid phase diffusion bonding). Alternatively, the bonding may be performed by ordinary welding by melting the heated portion to change to a state of a liquid phase. By these bonding methods, the bonding between the metal member and the member to be bonded under high-temperature conditions can be made stronger than, for example, in the case of bonding with a solder.

Some other examples of heating such as that in the JP 2014-228478 A The aim of this invention is to carry out a nondestructive investigation to determine whether a metal element and a member to be bonded which have already been bonded together are in contact and bonded together with a sufficient area therebetween. In technology of JP 2014-228478 A At first, a metal member is heated and its temperature is raised by irradiating a laser beam to the metal member to be bonded to a member to be bonded. At this time, when the metal member and the member to be bonded are in contact with each other with a sufficient area therebetween, the heat for increasing the temperature is satisfactorily transferred from the metal member to the member to be bonded, depending on the contact area. Accordingly, the temperature rise rate of the metal member is low. However, when the metal member and the member to be bonded are not in contact with a sufficient area therebetween, and they are insufficiently bonded together, the heat of the metal member can not be satisfactorily transferred to the member to be bonded, and thus the rate of temperature rise is high. Based on the difference between these temperature rise rates, the bonding state between the metal member and the member to be bonded is evaluated.

In the above description, as a radiated laser beam, in many cases, a low-cost YAG laser is used, for example. The YAG laser is a laser whose laser beam has a near-infrared wavelength (0.7 mm to 2.5 mm). The absorptivity of a metal element such as copper (or aluminum) for the laser beam emitted by the YAG laser is very low at a low temperature before reaching a predetermined temperature (eg, a melting point). Thus, for example, in the JP 4894528 . JP 5602050 . JP 2014-228478 A When a copper (or aluminum) is used for the metal member, the temperature rise of the metal member becomes low because the absorptivity of the metal member for the laser beam is low even when the laser beam is radiated directly onto the low-temperature metal member. Consequently, a lot of energy is consumed until the predetermined temperature is reached, from which the degree of absorption increases. Not only in copper or aluminum but also in other metals, generally at a low temperature, the temperature rise of the metal element is lower than at a high temperature, because the absorbance for the laser beam is lower. Consequently, a lot of energy is consumed until the predetermined temperature is reached, from which the degree of absorption increases.

In contrast, in the art of JP 2014-228478 A Based on known knowledge, an oxide film is formed on a surface of a metal member to increase the absorptivity of the metal member for a laser beam at low temperature. The oxide film is formed by irradiating a laser beam to form an oxide film on the surface of the metal member. In particular, to form the oxide film such that the film thickness thereof becomes a predetermined one Film thickness, which allows that a predetermined degree of absorption is obtained, the laser beam is irradiated to the surface of the metal element for a predetermined period of time. Subsequently, a heating laser beam is irradiated to the metal member through the thus formed oxide film. The temperature of the metal member whose laser beam absorbance is improved by the formation of the oxide film is rapidly increased, and the bonding state is effectively evaluated. In the JP 2014-228478 A From the known knowledge that the absorptance for the laser beam becomes saturated when the film thickness of the oxide film rises above a certain value, a film thickness at which the absorption degree is saturated is set, and the irradiation time of the laser beam for allowing this film thickness to be formed is adjusted.

However, it takes too much time to form an oxide film having a thickness equal to or greater than a certain film thickness with which the absorption degree becomes saturated, as in US Pat JP 2014-228478 A is described, which causes costs to rise. When the laser irradiation time is shortened to form the oxide film in a short time, the film thickness of the oxide film formed becomes thinner. In this case, a ratio between the film thickness of a thin oxide film which can be formed by laser irradiation for a short time and the absorptivity of the metal element for the laser beam has a periodicity in which a local maximum and a local minimum appear alternately in one construction in which the film thickness increases beyond 0. In this case, even if variations in the film thickness of the formed oxide film are not large and are small, large variations in the absorption degree occur. As a result, the degree of absorption for the laser beam can not be stably obtained although the cost is low.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a bonding method and a metal member bonding apparatus that can form a thin oxide film at a low cost to improve the absorptivity of a laser beam, thereby enabling bonding in a short time two metal elements can be obtained.

A bonding method according to one aspect of the present invention is a bonding method for bonding a first bonding surface of a first metal member to a second bonding surface of a second metal member in contact with the first bonding surface by radiating a hot bond laser beam to an irradiated surface of the first metal member to heat the first bonding surface.

The bonding process has:
an oxide film forming step of radiating a laser beam forming an oxide film at a first output on the irradiated surface of the first metal member and forming on the irradiated surface an oxide film having a film thickness corresponding to the first output and an irradiation time of the laser beam forming the oxide film;
a step of detecting a first reflected laser beam to detect a second output which is a output of a first reflected laser beam generated by the laser film forming laser due to being reflected by the irradiated surface;
a step of calculating a first absorptance, a first absorptance of the irradiated surface of the first metal element for the oxide film forming laser beam from the first output of the oxide film forming laser beam emitted in the oxide film forming step and the second output of the first reflected laser beam; which is detected in the step of detecting the first reflected laser beam;
a laser beam switching step of switching the oxide film forming laser beam irradiated on the irradiated surface to the hot bond laser beam if it is determined that the first absorbance is equal to or higher than a predetermined absorbance; and
a hot bonding step of, after switching to the hot bond laser beam, radiating the hot bond laser beam on the irradiated surface at a third output to heat the first bonding surface until a temperature of the first bonding surface reaches a predetermined bonding temperature and bonding the first bonding surface to the second bonding surface.

As described above, at the oxide film forming step, the laser beam forming the oxide film is irradiated on the irradiated surface of the first metal member. While the oxide film is formed on the irradiated surface, the first reflected laser beam reflected by the irradiated surface is detected, and the absorbance is calculated from the first output of the oxide film forming laser beam and the second output of the first reflected laser beam. In other words, the actual absorption degree for the oxide film forming laser beam obtained by the oxide film formed on the irradiated surface is obtained. When the absorptance for the laser film forming the oxide film is equal to or higher than the predetermined one Absorbance is, the oxide film forming laser beam is switched to the Warmbondlaserstrahl. The first bonding surface is then warmed to the predetermined bonding temperature in the warm bonding step, thereby bonding the first bonding surface to the second bonding surface. Thus, even if the irradiation time of the laser beam forming the oxide film is short, and only a thin oxide film can be formed, a desired absorptance can be reliably obtained. In other words, even with a thin oxide film formed in a short time at a low cost, the desired absorbance can be reliably obtained. As a result, the hot bond laser beam is absorbed by the first metal member having the desired absorptance, and the first bonding surface of the first metal member is warmed to the predetermined bonding temperature in a short time, so that the first bonding surface can be bonded to the second bonding surface in a short time.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention will be apparent from the following description of exemplary embodiments with reference to the accompanying drawings in which like reference numerals are used to represent like elements and in which:

1 an enlarged view of metal elements that are bonded together;

2 Fig. 12 is a graph showing a relationship between the wavelength of a near-infrared laser beam and the absorption degree by metal material;

3 Fig. 12 is a graph showing a relationship between the thickness of an oxide film and the laser beam absorption degree;

4 Fig. 12 is a graph showing a relationship between the film thickness of an oxide film formed on a surface of a metal member by irradiation with a laser beam forming an oxide film and the irradiation time;

5 FIG. 3 is a schematic diagram of a bonding apparatus according to a first embodiment; FIG.

6A Fig. 12 is a graph G1 showing a relationship between the radiation output of the oxide film forming laser beam and a hot bond laser beam and a time;

6B FIG. 12 is a graph G2 showing a relationship between the radiation output of the oxide film forming laser beam and the hot bond laser beam and a time; FIG.

6C FIG. 12 is a graph G3 showing a relationship between the radiation output of the oxide film forming laser beam and the hot bond laser beam and the time;

7 FIG. 10 is a flowchart of a bonding method according to the embodiment; FIG.

8th Fig. 11 is a conceptual diagram illustrating a state in which a metal element is heated from its surface by irradiation with a laser beam;

9 Fig. 10 is a schematic diagram of an apparatus body according to a second embodiment; and

10 FIG. 10 is a schematic diagram of an apparatus body according to a modification of the second embodiment. FIG.

DETAILED DESCRIPTION OF EMBODIMENTS

An outline of a bonding apparatus according to a first embodiment of the present invention will be described with reference to FIG 1 described. The bonding device is a device that bonds two metal elements by emitting a laser beam. As in 1 is illustrated, in the present embodiment, the two metal elements are a first metal element (lead frame 62 ), which is formed of copper, for example, and a second metal element (a metal terminal 51 on a surface of a semiconductor device 50 ), which is formed for example of gold.

In particular, the laser beam is irradiated to an illuminated surface 62a1 in a surface 62a of the lead frame 62 radiated. Thus, that causes the lead frame 62 the emitted laser beam from the irradiated surface 62a1 absorbed, reducing the lead frame 62 is heated. The temperature of a first bonding surface 62b facing the surface 62a of the lead frame 62 is elevated to a temperature to allow bonding.

Thus, the first bond surface 62b of the lead frame 62 facing the surface 62a is positioned, and a second bonding surface 51a in the upper surface of the metal terminal 51 connected as a terminal on the upper surface of the semiconductor device 50 is formed, bonded together. Before they are bonded, they are the first bonding surface 62b and the second bonding surface 51a in contact with each other. The semiconductor device becomes from its lower surface by a predetermined support member 52 supported.

In the present embodiment, as the laser beam is incident on the irradiated surface 62a1 of the lead frame 62 is emitted to the first bonding surface 62b to heat, uses a low-cost laser beam having a near-infrared wavelength, which will be described in detail later. For such a laser beam having a near infrared wavelength, copper has a very low absorptivity, which is the lead frame 62 formed. Thus, there is a problem here that it takes too much time, the first bonding surface 62b to heat by emitting the laser beam.

In consideration of this, in the present invention, in order to solve this problem, an oxide film OM having a film thickness α1 is formed on the irradiated surface 62a1 formed, whereby an absorption ability Y for the laser beam having a near-infrared wavelength is increased. As will be described in detail later, the fact that the formation of the oxide film OM increases the absorptivity for the laser beam as compared with the case without the oxide film OM is based on known knowledge. In the present embodiment, the oxide film OM is irradiated on the irradiated surface by irradiating the laser beam having a near infrared wavelength 62a1 educated.

In the present embodiment, it is assumed that the lead frame 62 and the metal connection 51 of the semiconductor device 50 be bonded together by known solid phase diffusion bonding. Solid-phase diffusion bonding is a known bonding process in which, for example, the first bonding surface 62b and the second bonding surface 51a in a solid state state with a pressure P1 in a pressure bonding direction against each other to be bonded together. The solid-phase state herein means a state that occurs at a temperature lower than the temperature of a liquid-phase state, and allows bonding in a solid state, and which, for example, by raising the temperature of the first bonding surface 62b of the lead frame 62 (first metal element) can be obtained.

In the solid-phase diffusion bonding, it has been found that a bonding (bond) having a high strength can be obtained by keeping the temperature of the first bonding surface to be bonded 62b for a certain period of time at a bonding temperature Ta, which is a temperature near the melting point of the lead frame 62 is and pressing the first bond surface 62b and the second bonding surface 51a in the Druckbondrichtung against each other. Solid phase diffusion bonding is just one example of bonding, and bonding is not limited thereto.

The following describes the absorptivity for a laser beam with reference to FIG 2 . 3 and 4 , 2 FIG. 11 is a general diagram illustrating a relationship between the wavelength of a laser beam and the absorptivity of the metal element. FIG. As in 2 In the present embodiment, copper used as the first metal member is a material whose absorption ability for a laser beam having a near infrared wavelength is very low at room temperature.

It is assumed in the present embodiment that as the first metal member, a low-absorbency material whose absorbance for the laser beam having a near-infrared wavelength is equal to or lower than a predetermined value at room temperature is adopted. The predetermined value of the absorbency is an absorption capacity of, for example, 30% (see FIG. 2 ). In this case, for example, copper or aluminum may be used as the low-absorbency material, and copper is used in the present embodiment.

In order to increase the absorbency, the inventors formed an oxide film OM on a surface of copper, and evaluated a relationship between the film thickness α of the oxide film OM and the absorptivity Y for the laser beam having a near infrared wavelength. 3 FIG. 15 is a graph showing a result of experiment which shows a relationship between the film thickness α (mm) of the oxide film OM formed on the surface (irradiated surface) of the copper and the absorbing ability Y (%) of the irradiated surface for the laser beam is a near-infrared wavelength α.

In the diagram of 3 The abscissa represents the film thickness α (nm) of the oxide film OM, and the ordinate represents the absorptivity (first absorptivity) Y1 (%) of the lead frame 62 for a laser beam L, when the laser beam hits the surface 62a of the lead frame 62 (Metal element) was emitted through the oxide film OM.

As in the diagram of 3 1, the first absorptivity Y1 has a periodicity in proportion to the film thickness α of the oxide film OM in which its normal local maximum values a and b (about 60%) and their local minimum values aa and bb (about 20 %) appear alternately with the change of the film thickness α in an upward direction, and also one Characteristic in which the first absorptivity Y1 is a local minimum when the film thickness α of the oxide film OM is zero. In other words, in the entire region of a region where the film thickness exceeds zero and the film thickness increases, the first absorptivity Y1 exceeds the absorptivity when the film thickness is zero.

Considering this, the inventors found that the first absorptivity Y1 of the oxide film OM on the irradiated surface 62a1 is formed having the periodicity in the ratio of the film thickness α, only within a first absorptivity range Ar2 corresponding to a first film thickness region Ar1a, in which the film thickness α of the oxide film OM exceeds zero and smaller than a first local minimum film thickness AA is. The first local minimum film thickness AA corresponds to the first local minimum value aa, which is the local minimum value of the first absorption capability Y1 between a first local maximum film thickness A corresponding to the first local maximum value a, which is the local maximum value of the Absorbance Y appears for the first time, and a second local maximum film thickness B corresponding to the second local maximum value b, which appears as a local maximum value of the first absorptivity Y1 following the first local maximum value a.

The inventors have thought that it is more preferable to set the first absorbing ability Y1 within a second absorbing ability range Ar3 in which the absorbing ability is equal to or higher than 40% of the first absorbing ability range Ar2. By this setting, the film thickness α corresponding to the second absorptivity range Ar3 ranges from 35 nm to 135 nm, and a sufficient range of the film thickness α can be obtained. Consequently, a first absorption ability Y1 of 40% or higher can be obtained stably.

As a condition of the experiment described above, the metal element was made of copper as described above. The laser beam L was radiated by a YAG laser, and was a laser beam having a near infrared wavelength. The oxide film OM was formed in an oven. In addition, the film thickness of the oxide film OM was measured by a sequential electrochemical reduction analysis (SERA). Thus, in the present embodiment, it is assumed that the film thickness of the oxide film OM is a film thickness measured by SERA in all cases.

The SERA is a well-known film thickness measurement method. In particular, to begin with, an electrolytic solution is applied to a metal surface, and a fine current is caused to flow from an electrode to cause a reduction reaction. At this time, the film thickness can be calculated by measuring the time required for the reduction because its substance has its own specific reduction potential.

4 FIG. 12 is a diagram showing an example of a relationship between an irradiation time H and the film thickness α of the oxide film OM formed when the near infrared wavelength laser beam is irradiated to a surface of a copper at an irradiation output Wx, eg

The following describes a configuration of a bonding apparatus 10 regarding 5 and 1 , As in 5 is shown, has the bonding device 10 a device body 20 , an oxide film formation control 30 and a warmbond control 40 , The oxide film formation control 30 controls the body of the device 20 That is, a laser beam L1 forming an oxide film, which will be described later in detail, on the surface 62a (irradiated surface 62a1 ) of the lead frame 62 to emit, thereby forming an oxide film OM.

The warmbond control 40 controls the body of the device 20 to emit a hot bond laser beam L3, which will be described later, on the oxide film OM exposed on the irradiated surface 62a1 is formed, and the first bonding surface 62b of the lead frame 62 with the second bonding surface 51a of the metal connection 51 to bond.

The device body 20 has a laser oscillator 21 , a laser head 22 , a housing 23 , a power meter 24 and a pusher 26 , The laser oscillator 21 causes the laser to oscillate at one wavelength and output according to the type of the laser, thereby producing a desired laser film L1 forming an oxide film. The wavelength of the laser film L1 forming the oxide film is preferably within a range of 0.7 μm to 2.5 μm. In other words, the laser film L1 forming the oxide film is preferably a laser beam having a near infrared wavelength, which is typically exemplified by the YAG laser.

In this case, the laser oscillator 21 be produced at low cost. Specifically, examples of the oxide film forming laser beam L1 that can be used include HoYAG (wavelength about 1.5 μm), yttrium vanadate (YVO, wavelength about 1.06 μm), ytterbium (Yb, wavelength about 1.09 μm), and fiber lasers one. The laser oscillator 21 has an optical fiber 25 through which the oxide film L1 forming laser beam to the laser head 22 is transmitted by the laser oscillator 21 is brought to oscillate.

A first output W1, which is an irradiation output of the oxide film forming laser beam L1, can be set to any order of magnitude. However, the first output W1 preferably has an intensity with which an oxide film OM having a film thickness α which enables the absorbing ability Y1 for the laser film L1 forming the oxide film to be obtained on the irradiated surface 62a1 of the lead frame 62 can be formed within a desired period of time.

As in 5 is pictured, is the laser head 22 in the case 23 is provided, provided at a predetermined distance from the surface 62a of the lead frame 62 by a predetermined distance and with respect to the surface 62a of the lead frame 62 is spaced by a predetermined angle γ °. The laser head 22 has a collimator lens 32 , a mirror 34 and a compressor lens 38 , The collimator lens 32 collimates the laser film L1 forming the oxide film, that of the optical fiber 25 is discharged, in parallel light. The mirror 34 changes the moving direction of the collimated oxide film L1 forming the oxide film such that the laser beam L1 forming the oxide film enters the compressor lens 38 entry. In the present embodiment, the mirror changes 34 the direction of movement of the oxide film forming laser beam L1 by 90 degrees. The compressor lens 38 densifies the parallel laser beam L1 forming the oxide film, that of the mirror 34 entry.

The power meter 24 detects a delivery of a first reflected laser beam L2. The first reflected laser beam L2 is a laser beam generated by the laser film L1 forming the oxide film facing the irradiated surface 62a1 is emitted when the oxide film forming laser beam through the irradiated surface 62a1 is reflected. When the oxide film OM on the irradiated surface 62a1 is formed, the first reflected laser beam L2 through the irradiated surface 62a1 reflected by the oxide film OM. The output of the first reflected laser beam L2 is a second output W2. The second output W2 is a value obtained by subtracting an absorbed output Wa, which is a portion of the output of the oxide film forming laser beam L1 passing through the lead frame 62 of the first output W1 which is the output of the laser film L1 forming the oxide film (W2 = W1 - Wa).

The first reflected laser beam L2 is from an input surface 24a of the power meter 24 entered. In other words, the power meter 24 is provided in an arbitrary position at an arbitrary angle such that the first reflected laser beam L2 as a whole is from the input surface 24a can be entered. Because the power meter 24 is a known measuring instrument that measures the output of a radiated laser beam, its detailed description is omitted. The output of the first reflected laser beam L2 can be measured not only by the power meter but also by a beam profiler, a CCD sensor or a CMOS sensor, for example.

The pusher 26 is a device that has the upper surface (surface 62a ) of the lead frame 62 pushes down. By pressing this, the pusher presses 26 the first bond surface 62b of the lead frame 62 heated to the bonding temperature Ta against the second bonding surface 51a to bond these surfaces together. The pressure with which the first bonding surface 62b to the second bonding surface 51a can be adjusted on the basis of test results which are carried out in advance. The pusher 26 may be any type of structure that has the first bonding surface 62b heated to the bonding temperature Ta against the second bonding surface 51a can press P1 with the pressure. The pressure P1 is a pressure with which the first bonding surface 62b heated to the bonding temperature Ta, to the second bonding surface 51a can be bonded.

The oxide film formation control 30 has a first laser beam matching radiation unit 41 (corresponding to a laser beam matching radiation unit), a first unit 43 for detecting a reflected laser beam, a unit 44 for calculating the first absorbing ability and a laser beam switching unit 45 ,

The first laser beam matching radiation unit 41 that is electrically connected to the laser oscillator 21 is connected, controls the wavelength and the output W of the laser beam passing through the laser oscillator 21 is oscillated and emitted. In particular, the first laser beam matching radiation unit causes 41 that the laser oscillator 21 causes the laser beam L1 forming the oxide film to oscillate, and the first output W1 to the irradiated surface 62a1 of the lead frame 62 (first metal element) is emitted. In this way, an oxide film OM having a film thickness α corresponding to the first output W1 and the irradiation time H of the laser film L1 forming the oxide film is formed on the irradiated surface 62a1 is trained (sh. 4 ).

The unit 43 for detecting the first reflected laser beam is electrically connected to the power meter 24 connected. From the power meter 24 The first unit for detecting the reflected laser beam receives data of the second output W2 of the first reflected laser beam L2 placed in the power meter 24 be entered. The unit 43 for detecting the first reflected laser beam transmits the received data of the second output W2 to the unit 44 for calculating the first absorption capacity.

From the first laser beam matching radiating unit 41 obtain the unit 44 for calculating the first absorptivity, the data of the first output W1 which is a output when the first laser beam matching radiation unit 41 that causes the laser oscillator 21 causes the laser film L1 forming the oxide film to oscillate and to the irradiated surface 62a1 is emitted. Starting from the first output W1 and the second output W2, that of the first unit 43 is acquired for detecting the reflected laser beam, the unit calculates 44 for calculating the first absorptivity, a first absorptivity Y1 indicative of the absorbance of the irradiated surface 62a1 of the lead frame 62 (First metal element) for the laser film L1 forming the oxide film. Here, the first absorptivity Y1 is calculated according to Y1 = (W1-W2) / W1. Data of the calculated first absorbing ability Y1 becomes the laser beam switching unit 45 transfer.

The laser beam switching unit 45 First, determine if the first absorbency Y1, that of the unit 44 for calculating the first absorptivity equal to or higher than, for example, 40%. When it is determined that the first absorbing ability Y1 is equal to or higher than 40%, the laser beam switching unit transmits 45 to the first laser beam matching radiating unit 41 a statement that irradiates the irradiated surface 62a1 from the laser film L1 forming the oxide film to the warm bond laser beam L3.

The following is the warmbond control 40 described. As in 5 pictured, has the warmbond control 40 a second laser beam matching radiation unit 42 , one unity 46 for detecting the second reflected laser beam, a unit 47 for calculating the second absorptivity, a laser beam output changing unit 48 and a pushing unit 49 , The second laser beam matching radiation unit 42 has the same function as the first laser beam matching radiating unit 41 the oxide film formation control 30 , Thus, their description is omitted.

The unit 46 for detecting the second reflected laser beam is in the same manner as the unit 43 for detecting the first reflected laser beam electrically with the power meter 24 connected. When the Warmbond laser beam L3 hits the radiated surface 62a1 is radiated with a third output B3, the unit detects 46 for detecting the second reflected laser beam with the power meter 24 a fourth output W4, which is the output of the second reflected laser beam L4 passing through the irradiated surface 62a1 is reflected. The oxide film L1 and the warm bond laser beam L3 forming the oxide film are the same types of laser beams, and both are laser beams each having a near-infrared wavelength.

Here, the incident angle of the warm bond laser beam L3 and the reflection angle of the second reflected laser beam L4 with respect to the irradiated surface are 62a1 the same as the incident angle of the laser film L1 forming the oxide film and the reflection angle of the first reflected laser beam L2 with respect to the irradiated surface, respectively 62a1 , The unit 46 for detecting the second reflected laser beam receives data from the fourth output W4 of the second reflected laser beam L4 passing through the power meter 24 were obtained from the power meter 24 , The unit 46 for detecting the second reflected laser beam transmits the received data of the fourth output W4 to the unit 47 for calculating the second absorption capacity.

Starting from the third output W3 and the fourth output W4 thus obtained, the unit calculates 47 for calculating the second absorption capacity, a second absorption capacity Y2 of the irradiated surface 62a1 of the lead frame 62 (first metal element) for the Warmbondlaserstrahl L3. Here, the second absorbance Y2 is calculated according to Y2 = (W3-W4) / W3. For example, when the second absorption ability Y2 increases, the fourth output W4 gradually decreases. As a factor in the change and increase of the second absorptivity Y2, one possible cause is, for example, the temperature of the irradiated surface 62a1 rises or the irradiated surface 62a1 melts. Thus, the temperature rise rate of the first bonding surface increases 62b because the warmbond laser beam L3 is in the lead frame 62 is absorbed more strongly. Data of the calculated second absorptivity Y2 becomes the laser beam output changing unit 48 transfer.

The laser beam output changing unit 48 adjusts the third output W3 based on the second absorptivity Y2, which coincides with the increase in the irradiation time H of the Warmbond laser beam L3 changes (increases). In particular, when the second absorptivity Y2 increases with lapse of time, the laser beam output changing unit transmits 48 to the second laser beam matching radiation unit 42 an instruction to reduce the third output W3 according to the increase.

The pushing unit 49 is electric with the pusher 26 connected. When the third output W3 by the laser beam output change unit 48 is controlled, and then the first bonding surface 62b has reached the bonding temperature Ta controls the pusher unit 49 the pusher 26 to the upper surface (surface 62a ) of the lead frame 62 to press downwards with the pressure P1. Thus, the first bonding surface becomes 62b against the second bond surface 51a pressed and bonded. The pressure P1 for this pressing may be set based on comparative experiments performed in advance, as described above.

Herein, the laser beam output changing unit 48 adjust the third output W3 in an optional manner. As in the diagram G1 of 6A 1 is a relationship between the first and third outputs W1 and W3 and the elapsed time, the third output W3 can be linearly reduced. Alternatively, as in the diagram G2 of 6B 1, the third output W3 is reduced along a curve. In addition, as shown in diagram G3 of 6C is shown, the third output W3 gradually reduced.

While the third output W3 is adapted to decrease as described above, the first bonding surface becomes 62b is heated until its surface reaches the predetermined bonding temperature Ta, which allows the temperature of the first bonding surface 62b simply kept at the bonding temperature Ta near the melting point. Thus, because of the reason described above, the protrusion of the bonding having a high bonding strength can be easily obtained in the solid-phase diffusion bonding.

The following is a bonding method using the bonding apparatus 10 with reference to the flowchart in FIG 7 and 8th described. As in the flowchart in 7 1, the bonding method has an oxide film thickness adjustment step S1 and a warm bonding step S3. The oxide film thickness adjusting step S1 has an oxide film forming step S10, a step S12 detecting a first reflected laser beam, a step S14 calculating a first absorbing ability, and laser beam switching steps S16A and S16B. The warm bonding step S3 has a laser beam matching radiation step S30, a second reflected laser beam detection step S32, a second absorptivity calculation step S34, laser beam output changing steps S36A, S36B and S36C, and a pressing step S38.

In the oxide film forming step S10 of the oxide film thickness adjusting step S1, the first laser beam matching radiation unit causes 41 For example, if a start button (not shown) of the bonding device 10 is depressed by an operator that the laser oscillator 21 causes the laser beam L1 forming the oxide film to oscillate and from the laser head 22 on the surface 62a (irradiated surface 62a1 ) of the lead frame 62 (first metal element) is emitted. Through this irradiation is on the irradiated surface 62a1 An oxide film OM having a film thickness α corresponding to the first output W1 and the irradiation time H through the oxide film forming laser beam L1 is formed.

At the irradiated surface 62a1 For example, the laser beam L1 forming the oxide film as the first reflected laser beam L2 becomes an in 1 reflected direction. At this time will be at the irradiated surface 62a1 a discharge (Wa) which is a portion of the first output W1 of the oxide film forming laser beam L1 is absorbed, and the first reflected laser beam L2 is reflected at the remaining second output W2.

At the step S12 for detecting the first reflected laser beam, the unit detects 43 for detecting the first reflected laser beam, the second output W2 of the first reflected laser beam L2 with the power meter 24 , The unit 43 for detecting the first reflected laser beam transmits data of the detected second output W2 to the unit 44 for calculating the first absorption capacity.

At the first absorbing ability calculating step S14, the unit acquires 44 for calculating the first absorptivity, data from the first output W1 of the oxide film forming laser beam L1 from the first laser beam matching radiation unit 41 , Starting from the first output W1 and the second output W2, by the unit 43 for acquiring the first reflected laser beam, the unit calculates 44 for calculating the first absorbency, the first absorbency Y1, the absorbency of the irradiated surface 62a1 (First metal element) for the oxide film forming laser beam L1 according to Y1 = (W1 - W2) / W1.

At the laser beam switching step S16A, first, the laser beam switching unit determines 45 , if the first absorbing ability Y1 is equal to or higher than an absorbing ability Ya (eg, 40%) corresponding to a predetermined absorbing ability. If it is determined that the first absorptivity Y1 is equal to or higher than 40% at the laser beam switching step S16B (in the oxide film thickness adjustment step S1), the laser beam switching unit transmits 45 an instruction to switch the laser beam to the first laser beam matching radiation unit 41 , In response to the instruction, the first laser beam matching radiation unit switches 41 the radiation on the irradiated surface 62a1 from the oxide film forming laser beam L1 to the hot bond laser beam L3. However, if the laser beam switching unit 45 determines that the first absorbing ability Y1 is lower than 40%, the process returns to step S12 for detecting the first reflected laser beam. Subsequently, the processes from S12 to S16A are repeated until it is determined at the laser beam switching step S16A that the first absorbing ability Y1 is equal to or higher than the absorbing ability Ya.

The following describes the warm bonding step S3. As described above, the warm bonding step S3 has the laser beam matching irradiation step S30, the second reflected laser beam detection step S32, the second absorption ability calculation step S34, the laser beam output changing step S36A, S36B and S36C, and the pressing step S38.

The process at the laser beam matching radiation step S30 is almost the same as that at the oxide film forming step S10 of the oxide film thickness adjusting step S1. The second laser beam matching radiation unit 42 that causes the laser oscillator 21 causes the warm bond laser beam L3 to oscillate and to the third output W3 from the laser head 22 on the irradiated surface 62a1 of the lead frame 62 (First metal element) is radiated through the oxide film OM, which allows an absorption capacity of 40% or more.

At this time, the third output W3 is set to a value smaller than that of the first output W1, which is the output of the emitted oxide film formation laser beam L1 (W1> W3). This setting can cause a sudden temperature increase of the lead frame 62 (first bond surface 62b ). At the irradiated surface 62a1 the second reflected laser beam L4 of the warm bond laser beam L3 is inserted into the in 1 and 5 reflected directions.

While being performed by or reflected by the oxide film OM formed so that the first absorbing ability becomes 40% or higher, for example, the warm bond laser beam L3 becomes effective in the surface 62a of the lead frame 62 absorbs and satisfactorily heats the lead frame 62 , In particular, as in 8th is shown, the lead frame is heated so that heat from the surface 62a to the back (first bond surface 62b ), which is opposite to the surface 62a is positioned until the temperature of the first bonding surface 62b finally reaches the bonding temperature Ta. Section D in 8th makes an image of the lead frame 62 that is from the surface 62a to the first bond surface 62b is heated, the heat transfer is represented by an area with oblique lines whose thickness is different from that of the oblique lines, the cross section of the lead frame 62 Show.

At the step S32 for detecting the second reflected laser beam, the unit detects 46 for detecting the second reflected laser beam, the fourth output W4 with the power meter 24 , Subsequently, the unit transmits 46 for detecting the second reflected laser beam, data of the fourth output W4 to the unit 47 for calculating the second absorption capacity.

At the second absorptivity calculation step S34, based on the third output W3 and the fourth output W4, which has been obtained, the second absorbance Y2 of the irradiated surface is determined 62a1 of the lead frame 62 (first metal element) calculated for the Warmbondlaserstrahl L3. Especially in the same way as the unit 44 for calculating the first absorption capacity, the unit calculates 47 for calculating the second absorption capacity from the third delivery W3 and the fourth delivery W4, the second absorption capacity Y2, which is the absorption capacity of the irradiated surface 62a1 of the lead frame 62 (first metal element) for the hot bond laser beam L3 according to Y2 = (W3 - W4) / W3.

At the load beam output changing step S36A, the laser beam output changing unit calculates 48 the third output W3 corresponding to the second absorptivity Y2, which changes with the increase of the irradiation time H of the warm bond laser beam L3.

Subsequently, at the laser beam output changing step S36B to irradiate the warm bond laser beam L3 at the calculated third output W3, command values corresponding to the third output W3 to the second laser beam matching radiation unit 42 transfer. In particular, when the second absorbing ability Y2 increases with the lapse of time, the third becomes Release W3 is reduced with the lapse of time, and the second absorption capacity Y2 increases.

Any type may be used at this time to reduce the third output W3. For example, a third output can be reduced, as in diagrams G1 to G3 of FIG 6A to 6C is pictured, which have been described above. Through this adjustment, when the Warmbondlaserstrahl L3 on the irradiated surface 62a1 is emitted to the first bonding surface 62b to heat, the temperature rise rate of the first bonding surface 62b be satisfactorily limited.

In other words, the temperature of the first bonding surface 62b can easily at the bonding temperature Ta near the melting point of the lead frame 62 can be held, and a high bonding strength can be between the first bonding surface 62b and the second bonding surface 51a to be obtained.

Subsequently, at the laser beam output changing step S36C, it is determined whether the temperature T (estimated temperature) of the first bonding surface 62b was raised to the bonding temperature Ta. At this time, the temperature of the first bonding surface 62b for example, based on the third output W3 and the irradiation time H are estimated. However, the estimate is not limited to that but the temperature of the first bonding surface 62b can be based on the temperature of the irradiated surface 62a1 after measuring the temperature of the irradiated surface 62a1 with a thermometer (not shown) such as an infrared thermometer.

If it is determined that the temperature of the first bonding surface 62b has been raised to the bonding temperature Ta, the process proceeds to the pressing step S38. If it is determined that the temperature of the first bonding surface 62b is not raised to the bonding temperature Ta, the process returns to the second reflected laser beam detection step S32. Subsequently, the processes from S32 to S36C are repeated until the temperature of the first bonding surface is determined at the laser beam output changing step S36C 62b was raised to the bonding temperature Ta.

At the pressing step S38, the pressing unit controls 49 the pusher 26 to the surface 62a of the lead frame 62 to press downwards with the pressure P1. This push becomes the first bonding surface 62b in the residual phase state to the second bonding surface 51a bonded.

In the present embodiment, a description has been given on the assumption that the pressing unit 49 controls, pushing the lead frame 62 (first metal element) at the pressing step S38 after the temperature of the first bonding surface 62b has reached the predetermined bonding temperature Ta, but the initial time is not limited to this. This through the control of the pressing unit 49 Presses performed may be started at any time within the time period after the warm bond laser beam L3 hits the irradiated surface 62a1 was radiated to the heating of the first bonding surface 62b at the laser beam matching radiating step S30 until the temperature of the first bonding surface 62b reaches the predetermined bonding temperature. This through the control of the pressing unit 49 Performed pressing can also be started before the Warmbondlaserstrahl L3 on the irradiated surface 62a1 is emitted at the laser beam matching radiation step S30. This through the control of the pressing unit 49 Pressing performed may also be started before the laser film L1 forming the oxide film is irradiated to the irradiated surface 62a1 is emitted. In this case, the bonding strength can be easily controlled. As a pressing member, any element can be used. The pressure P1 applied here, which is a pressure that enables the solid-phase diffusion bonding to be obtained, is examined in advance and determined.

In the bonding method described above, a mode has been described in which the first bonding surface 62b and the second bonding surface 51a bonded together by solid-phase diffusion bonding, but the bonding method is not limited to this mode. As an alternative bonding method, the first bonding surface 62b and the second bonding surface 51a after they are heated until the state thereof is changed to the liquid phase state (molten state). In this case, in the warm bonding step S3, the second reflected laser beam detection step S32, the second absorptivity calculation step S34, the laser beam output changing steps S36A to S36C, and the pressing step S38 may be omitted. The third output W3 of the warm bond laser beam L3 at the laser beam matching radiation step S30 may be on the order of the same as the first output W1 of the laser film L1 forming the oxide film. The third output W3 may be greater than the first output W1. Thus, the bonding between the first bonding surface 62b and the second bonding surface 51a be completed in a shorter time.

At the oxide film thickness adjustment step S1 of the above-described bonding method, the predetermined absorptivity Ya is calculated from the graph of FIG 3 which is a ratio between the film thickness α and the first absorptivity Y1 of the oxide film OM. However, the setting is not limited to this. The absorbency Ya can be easily adjusted to a desired absorbency not shown on the diagram of FIG 3 based. It should be noted herein that when the film thickness α of the oxide film OM is small, the first absorptivity Y1 with respect to the film thickness α of the oxide film OM has a characteristic in which a local maximum value and a local minimum value appear alternately , Thus, there are cases when the desired absorbency is excessively high and exceeds the local maximum value in which the absorbency Ya can not be adjusted. Considering this, the adjustment must be made.

In the bonding method described above, it is assumed that the absorbing ability Ya used as a criterion for determining whether the first absorbing ability Y1 is equal to or higher than the absorbing ability Ya at the laser beam switching step S16A (oxide film thickness adjusting step S1) is set to 40%. However, the setting is not limited to this. The absorbency Ya can be set at 60%, which is the first local maximum value a in the graph of FIG 3 is. In this case, the corresponding film thickness α of the oxide film OM is limited to the point A, which makes its control difficult, but the maximum absorbing ability can be obtained. In this case, at the warm bonding step S3, the warm bond laser beam L3 is in the lead frame 62 absorbed, and the first bonding surface 62b is heated to the bonding temperature Ta in a shorter time. In the diagram of 3 For example, the absorbing ability Ya within the first absorbing ability range Ar2 (about 20% to 60%) may be set according to the first film thickness range Ar1a. In this case also reasonable effects can be obtained.

In the bonding method described above, it is assumed that the film thickness α of the oxide film OM corresponding to the absorptivity Ya as a criterion for determining the first absorptivity Y1 at the laser beam switching step S16A (oxide film thickness adjustment step S1) falls within the first film thickness region Ar1a. However, the range is not limited to this. The range of the film thickness α of the oxide film OM corresponding to the absorptivity Ya may be a wider range in which not only the first film thickness region Ar1a but also a second film thickness region Ar1b is counted.

As in 3 In this case, the second film thickness area Ar1b has values equal to or larger than the first local minimum film thickness AA. The second film thickness area Ar1b has the second local maximum film thickness B corresponding to the second local maximum value B, which appears as the local maximum value of the first absorptivity Y1, subsequently to the first local maximum value A. Moreover, the second film thickness area is located Ar1b at an area smaller than the second local minimum film thickness BB corresponding to the second local minimum value bb appearing as the local minimum value of the first absorptivity Y1, between the second local maximum film thickness B and a third local maximum Film thickness C corresponding to the third local maximum value c appearing as the local maximum value of the first absorptivity Y1 subsequent to the second local maximum value b. By setting the predetermined absorbing ability Ya to correspond to a film thickness falling within the film thickness region of the oxide film OM which is a combination of the first film thickness region Ar1a of the second film thickness region Ar1b, the possibility that the film thickness α becomes excessively large and the desired film thickness can not be adjusted, be excluded.

The following describes a bonding apparatus according to a second embodiment with reference to FIG 9 , The device body 20 According to the first embodiment described above, it is so configured that the oxide film L1 forming the oxide film is applied to the surface 62a as a lead frame 62 is radiated through the oxide film OM, and then the first reflected laser beam L2 passing through the irradiated surface 62a1 in the surface 62a of the lead frame 62 is reflected, directly through the power meter 24 Will be received.

As in 9 pictured has a device body 200 according to the second embodiment, in contrast, a dichroic mirror 110 on the optical axis of the laser film L1 (and the hot bond laser beam L3) forming the oxide film. The dichromatic mirror 110 is an element that reflects light of a certain wavelength range (eg, a near-infrared wavelength) and allows the light of the other wavelength range to pass through. Not only the dichromatic mirror, but any element having such a property may be used instead.

As described above, the apparatus body is 200 from the device body 20 according to the first embodiment characterized in that the dichromatic mirror 110 on the optical path of the oxide film forming laser beam L1 (Warmbondlaserstrahl L3) is provided, and the oxide film forming laser beam L1 (Warmbondlaserstrahl L3) on the surface 62a (irradiated surface 62a1 ) of the lead frame 62 at right angles to it is incidental. Thus, only different portions will be described and the description of the same portions will be omitted. The same components are denoted by the same reference numerals in the following description.

As in 9 pictured is the dichromatic mirror 110 between the laser head 22 and the surface 62a (irradiated surface 62a1 ) of the lead frame 62 provided on the optical axis of the oxide film forming laser beam L1 (Warmbondlaserstrahl L3), by about 45 degrees with respect to the surface 62a to be tipped. In the second embodiment, in which the dichroic mirror 110 Thus, the laser film L1 forming the oxide film (hot bond laser beam L3) from the laser head becomes 22 which is provided so that the optical axis of the oxide film forming laser beam L1 is horizontal, to the dichroic mirror 110 radiated.

A large part of the laser film forming the oxide film L1 (Warmbondlaserstrahl L3), the dichromatic mirror 110 has achieved through a mirror surface 110a the dichromatic mirror 110 and part of it passes through the dichromatic mirror. The oxide film L1 forming the oxide film (Warmbond laser beam L3) passing through the mirror surface 110a is reflected, whose direction of movement is changed to a direction perpendicular thereto, falls on the surface 62a (irradiated surface 62a1 ) of the lead frame 62 perpendicular to the surface 62a (irradiated surface 62a1 ) one.

Subsequently, a part of the oxide film forming laser beam L1 (Warmbondlaserstrahl L3) in the lead frame 62 from the surface 62a absorbed to be converted into heat. The remaining part of it is through the irradiated surface 62a1 reflects and moves as the first reflected laser beam L2 (second reflected laser beam L4) as the one to the game surface 110a the dichromatic mirror 110 around the mirror surface 110a to reach, which is provided so that it with respect to the irradiated surface 62a1 is tilted. At this time is through the mirror surface 110a the dichromatic mirror 110 , which has reached the first reflected laser beam L2 (second reflected laser beam L4), reflects a large part of the first reflected laser beam L2 (second reflected laser beam L4) again, and moves parallel to the optical axis of the oxide film forming laser beam L1 (Warmbond laser beam L3 ) to the laser head 22 ,

From the mirror surface 110a When the first reflected laser beam L2 (second reflected laser beam L4) has reached, a part of the first reflected laser beam L2 (second reflected laser beam L4) passes through the dichroic mirror 110 to get in 9 to move upwards. Subsequently, this penetrating laser beam L5 (first reflected laser beam L2, second reflected laser beam L4) enters the input surface 24a of the above provided power meter 24 is input, and the output (second output W2, fourth output W4) of the passing laser beam L5 (first reflected laser beam L2, second reflected laser beam L4) is detected.

By this configuration, similarly to the first embodiment, the first and second absorption capacities Y1 and Y2 of the irradiated surface can be made 62a1 on which the oxide film OM is formed can be accurately detected. When the first absorbing ability Y1 has become equal to or higher than the predetermined absorbing ability Ya, the laser film L1 forming the oxide film is switched to the warm bond laser beam L3 in the same manner as in the first embodiment. Subsequently, by the same steps as those in the first embodiment, the first bonding surface 62b of the lead frame 62 (first metal element), then the second bonding surface 51a of the metal connection 51 (second metal element) on the surface of the semiconductor device 50 bonded. With this configuration, too, the same effects as those in the first embodiment can be obtained.

In the second embodiment, unlike the first embodiment, the laser head 22 be provided horizontally, and thus the configuration is simple. Since the output of the passing laser beam L5 (first reflected laser beam L2, second reflected laser beam L4), which in the power meter 24 is small, a compact power meter can be used, which contributes to a cost reduction. Since the oxide film forming the oxide film L1 (Warmbondlaserstrahl L3) at right angles to the irradiated surface 62a1 can be incidental, the first and second absorption capacities Y1 and Y2 can be accurately obtained.

The present embodiment is not limited to the second embodiment. As a modification of the second embodiment, a dichromatic mirror 210 , the laser head 22 and the power meter 24 be provided as in 10 is shown. In this modification is the dichromatic mirror 210 between the laser head 22 which has its optical axis arranged in the vertical direction, and the surface 62a of the lead frame 62 Namely, on the optical axis of the oxide film forming laser beam L1 (Warmbondlaserstrahl L3), so that it by about 45 degrees with respect to the surface 62a (irradiated surface 62a1 ) is tilted. The dichromatic mirror 110 and the dichromatic mirror 210 differ in the manner of passing or reflection of the laser film forming the oxide film L1 (Warmbondlaserstrahl L3).

In the modification in which the dichromatic mirror 210 is thus provided, as in 10 1, the laser beam L1 (hot bond laser beam L3) forming the oxide film becomes the laser head 22 which is provided so that the optical axis thereof is vertical, to the dichroic mirror 210 radiated.

Much of the oxide film forming laser beam L1 (Warmbondlaserstrahl L3), the dichromatic mirror 210 has reached, passes through a mirror surface 210a the dichromatic mirror 210 by. The oxide film L1 forming the oxide film (Warmbond laser beam L3) passing through the mirror surface 210a passes, reaches (is incident on) the surface 62a (irradiated surface 62a1 ) of the lead frame 62 at right angles to it.

Subsequently, a part of the oxide film forming laser beam L1 (Warmbondlaserstrahl L3) in the lead frame 62 from the surface 62a (irradiated surface 62a1 ) to be converted into heat. The remaining part thereof is referred to as the first reflected laser beam L2 (second reflected laser beam L4) through the surface 62a (irradiated surface 62a1 ) and moves back to a mirror surface 210b the dichromatic mirror 210 to the mirror surface 210b to achieve that is provided so that they are 45 degrees with respect to the surface 62a is tilted.

At this time is through the mirror surface 210b the dichromatic mirror 210 , which has reached the first reflected laser beam L2 (second reflected laser beam L4), reflects a part of the first reflected laser beam L2 (second reflected laser beam L4) at a right angle, and moves to the power meter 24 , Subsequently, this first reflected laser beam L2 (second reflected laser beam L4) becomes the input surface 24a of the power meter 24 entered in 10 is provided on the left, and the output thereof (second output W2, fourth output W4) is detected. By this configuration, similarly to the first embodiment, the first and second absorption capacities Y1 and Y2 of the irradiated surface can be made 62a1 are detected, on which the oxide film OM is formed. With this configuration, too, the same effects as those in the first embodiment can be obtained.

In this modification, unlike the first embodiment, the laser head 22 be provided vertically, and thus the configuration is simple. Similar to the second embodiment, since the output of the first reflected laser beam L2 (second reflected laser beam L4) incorporated in the power meter 24 is small, a compact power meter can be used, which contributes to a cost reduction. Since the oxide film forming the oxide film L1 (Warmbondlaserstrahl L3) on the irradiated surface 62a1 at right angles thereto, the first and second absorption capacities Y1 and Y2 can be accurately obtained.

In the above-described embodiments, a description has been given on the assumption that the relationship between the first output W1 of the oxide film forming laser beam L1 and the third output W3 of the warm bond laser beam L3 is given as W1> W3. However, the ratio is not limited to that, and the ratio between the first output W1 and the third output W3 may be given as W1 = W3. Alternatively, the ratio between the first output W1 and the third output W3 may be given as W1 <W3. In these cases, attention is required to prevent the temperature of the first bonding surface 62b of the lead frame 62 overly increases in a short time. If the temperature excessively increases in a short time, the bonding strength may fail to meet a predetermined strength value in the case of solid-phase diffusion bonding. This possibility is excluded if the bonding between the first metal element and the second metal element is performed by welding instead of the solid-phase diffusion bonding.

The bonding device 10 and the bonding method described above have been described by radiating the warm bond laser beam L3 while adjusting the third output W3 of the warm bond laser beam L3 to decrease. However, the adjustment is not limited to this. The third output W3 can be constant. Alternatively, the warm bond laser beam L3 may be radiated while the third output W3 is adjusted to increase. In these cases, reasonable effects can also be obtained.

In the above-described embodiments, copper is used as the first metal element which is a low-absorbency material. However, the first metal member is not limited to this, and a material other than a low-absorbency material may be used as the first metal member. In this case, too, similar effects to those in the above-described embodiments can be expected.

According to the above-described embodiments, the bonding method for a metal member is a bonding method for bonding the first bonding surface 62b of the lead frame 62 (first metal element) to the second bonding surface 51a of the semiconductor device 50 (second metal element) connected to the first bonding surface 62b by radiating the Warmbond laser beam L3 onto the irradiated surface 62a1 of the lead frame 62 to the first bonding surface 62b to warm up. The bonding method has: the oxide film forming step S10, the laser beam L1 forming the oxide film on the first output W1 on the irradiated surface 62a1 of the lead frame 62 to radiate, and forming on the irradiated surface 62a1 an oxide film OM having a film thickness corresponding to the first output W1 and the irradiation time of the laser film L1 forming the oxide film; the step S12 of detecting the first reflected laser beam to detect the second output W2 which is a output of the first reflected laser beam L2 emitted from the laser film L1 forming the oxide film due to being reflected by the irradiated surface 62a1 is produced; the step S14 to calculate the first absorbing ability, the first absorbing ability Y1 of the irradiated surface 62a1 of the lead frame 62 for the oxide film L1 forming the oxide film, starting from the first output W1 of the oxide film forming laser beam L1 radiated in the oxide film forming step S10, around the second output W2 of the first reflected laser beam L2 detected in the first reflected laser beam detecting step S12 was calculated; the laser beam switching steps S16A and S16B, the laser film L1 forming the oxide film, on the irradiated surface 62a1 is radiated to switch to the warm bond laser beam L3 where it is determined that the first absorptivity Y1 is equal to or higher than the predetermined absorbance Ya; and the warm bonding step S3, after switching the warm bond laser beam L3, the warm bond laser beam L3 with the third output W3 to the irradiated surface 62a1 to radiate to the first bonding surface 62b to heat until its temperature reaches the predetermined bonding temperature Ta, and the first bonding surface 62b to the second bonding surface 51a to bond.

As described above, in the oxide film forming step S10, in the oxide film thickness adjusting step S1, the laser beam L1 forming the oxide film becomes the irradiated surface 62a1 of the lead frame 62 (first metal element) radiated. While the oxide film OM on the irradiated surface 62a1 is formed, the second output W2 of the first reflected laser beam L2, by the irradiated surface 62a1 is reflected, recorded, and the absorption capacity of the irradiated surface 62a1 calculated from the first output W1 of the oxide film forming the oxide film L1 and the second output W2 of the first reflected laser beam L2. In other words, the actual first absorbing ability Y1 obtained by the oxide film OM on the irradiated surface is obtained 62a1 is trained.

When the first absorptivity Y1 for the oxide film L1 forming the oxide film becomes equal to or higher than the absorptivity Ya, the oxide film L1 forming the oxide film is switched to the warm bond laser beam L3. The first bond surface 62b is then heated to the bonding temperature Ta by blasting the warm bond laser beam L3, thereby forming the first bonding surface 62b to the second bonding surface 51a is bonded. Thus, even if the irradiation time of the oxide film L1 forming the oxide film is short and only a thin oxide film OM can be formed, the desired first absorptivity Y1 can be reliably obtained. As a result, the warm bond laser beam L3 passes through the lead frame 62 (first metal element) having the desired first absorptivity Y1 absorbed, and the first bonding surface 62b of the lead frame 62 is warmed up to the predetermined bonding temperature in a short time. Thus, the first bonding surface 62b to the second bonding surface 51a be bonded in a short time.

According to the embodiments, in the bonding method for a metal element, the bonding temperature Ta is a temperature at which the first bonding surface 62b and the second bonding surface 51a be placed in a solid phase state that occurs at a temperature lower than a temperature of a liquid phase state, and allows bonding therebetween in a solid state. At the warmbond step S3 become the first bond surface 62b and the second bonding surface 51a in the solid state state in the press bonding direction against each other to be bonded together. Because the first bond surface 62b and the second bonding surface 51a bonded together by solid-phase diffusion bonding, the temperature of the first bonding surface must be 62b not be raised to a high temperature when the bonding surface is heated. Thus, the energy required to raise the temperature can be reduced, which is efficient.

According to the embodiments, the third output W3 of the warm bond laser beam L3 radiated in the warm bonding step S3 is lower than the first output W1 of the laser film L1 forming the oxide film. This setting can increase the temperature of the first bond surface 62b of the lead frame 62 , which is heated by the radiation of the Warmbondlaserstrahls L3, be made slow. Thus, the temperature of the first bonding surface 62b simply at a temperature which is the predetermined bonding temperature Ta near the melting point, held for a predetermined period of time. This is suitable for performing the solid-phase diffusion bonding, which enables to obtain a bonding having a high bonding strength by keeping the bonding surface in the solid state state near the melting point for a predetermined period of time.

According to the embodiments, in the relationship with the film thickness α of the oxide film OM, the absorptivity Y has a periodicity in which its local maximum values and its local minimum values aa and bb appear alternately with the change of the film thickness α in a rising direction, and also has a property in which the absorbency Y is minimum when the film thickness α of the oxide film OM is zero. The predetermined absorbance Ya at the laser beam switching step S16A having the periodicity in proportion to the film thickness is set within the first absorbance region Ar2 corresponding to the first film thickness region Ar1a in which the film thickness α of the oxide film OM exceeds zero and smaller than the first local minimum thickness. Film thickness is AA. The first local minimum film thickness AA corresponds to the first local minimum value aa, which appears as the local minimum value of the first absorptivity Y1 between the first local maximum film thickness A corresponding to the first local maximum value a, which is the local maximum value of the first absorbance Y1 for the first time, and the second local maximum film thickness B corresponding to the second local maximum value b appearing as a local maximum value of the first absorbance Y1 subsequent to the first local maximum value a.

In this way, based on the ratio between the first absorptivity Y1 and the film thickness α of the oxide film OM prepared in advance, the predetermined absorptivity Ya used as a criterion for the determination in the laser beam switching step S16A is set. Thus, a time consumption for e.g. Setting the predetermined absorption capacity Ya to a non-existent absorbency, which exceeds the local maximum values a and b are removed.

According to the embodiments, the predetermined absorptivity Ya used in the laser beam switching step S16A as a criterion for determining the first absorptivity Y1 is set to 40%. In other words, the first absorptivity Y1 is equal to or higher than 40%. Thus, the film thickness α drops from the ratio between the film thickness α of the oxide film OM and the first absorptivity Y1 having a periodicity in which the local maximum values a and b and the local minimum values aa alternate with the change of the film thickness α appear in a rising direction within a predetermined range (35 nm to 135 nm), and thus can be easily adjusted.

According to the embodiments, in the relationship between the film thicknesses α of the oxide film OM and the first absorptivity Y1 corresponding to those in FIG 3 has the periodicity shown, the range of the first absorptivity Y1 corresponding to the film thickness α of the oxide film OM in the first film thickness region Ar1a and in the second film thickness region Ar1b of 20% to 60%. In this way, sufficiently high absorptivities within the width range of the film thickness α can be obtained. Thus, although depending on the value of the predetermined absorptivity Ya used for the determination, if it is determined whether to switch to the laser beam L1 forming the oxide film, the determination condition is relatively not strict, and thus can be easily satisfied.

According to the second embodiment and the modification, at the oxide film forming step S10, the laser beam L1 forming the oxide film is on the irradiated surface 62a1 incident to it at right angles. Thus, the absorbency of the irradiated surface 62a1 be obtained exactly.

According to the embodiments, the bonding method has: in the warm bonding step S3, the second reflected laser beam detection step S32 to detect the fourth output W4 which is the output of the second reflected laser beam L4 resulting from the warm bond laser beam L3 with the third output W3 on the irradiated surface 62a1 is emitted due to being reflected by the irradiated surface 62a1 ; and the step of calculating the second absorptivity, the second absorbance Y2 of the irradiated surface 62a1 of the lead frame 62 (first metal element) for the warm bond laser beam L3 from the third output W3 and the fourth output W4. By doing Warm bonding step S3, the third output W3 is adapted from the second absorptivity Y2, which changes with the increase in the irradiation time H of the Warmbondlaserstrahls L3.

This adaptation allows the temperature of the first bonding surface 62b are simply kept at a temperature, the bonding temperature Ta is near the melting point for a predetermined period of time. Thus, as described above, in the solid-phase diffusion bonding, excellent bonding having a high bonding strength can be obtained.

According to the embodiments, the bonding device is 10 a bonding device, the Warmbondlaserstrahl L3 on the irradiated surface 62a1 of the lead frame 62 (first metal element) radiates to the first bonding surface 62b of the lead frame 62 to warm up, and thereby the first surface 62b to the second bonding surface 51a of the metal connection 51 (second metal element) to be bonded to the first bonding surface 62b is in contact. The bonding device 10 has: the first laser beam matching radiation unit 41 , the laser beam L1 forming the oxide film on the irradiated surface 62a1 of the lead frame 62 with the first output W1 radiates to the irradiated surface 62a1 to form the oxide film OM having a film thickness α corresponding to the first output W1 and the irradiation time H of the laser film L1 forming the oxide film; the unit 43 for detecting the first reflected laser beam detecting the second output W2 which is the output of the first reflected laser beam L2 emitted from the laser film L1 forming the oxide film due to being reflected by the irradiated surface 62a1 is produced; the unit 44 for calculating the first absorption capacity, the first absorption capacity Y1 of the irradiated surface 62a1 of the lead frame 62 for the laser film L1 forming the oxide film, calculated from the first output W1 and the second output W2; the laser beam switching unit 45 that the laser film L1 forming the oxide film, that on the irradiated surface 62a1 is switched to the Warmbondlaserstrahl L3 switches, if it is determined that the first absorption capacity Y1 is equal to or higher than the predetermined absorption capacity; and the warmbond control 40 in that after switching to the warm bond laser beam L3 the hot bond laser beam L3 with the third output W3 is applied to the irradiated surface 62a1 radiates to the first bonding surface 62b to heat until its temperature reaches the predetermined bonding temperature Ta, and the first bonding surface 62b to the second bonding surface 51a Bondet. With this configuration, when the metal members are bonded together, a bonding having the same effects as those described in the embodiments can be obtained.

According to the embodiments, the unit detects 42 for detecting the first reflected laser beam, the second output W2 of the first reflected laser beam L2 with the power meter 24 , By this configuration, the first absorption ability Y1 of the irradiated surface can be 62a1 are accurately calculated for the laser film L1 forming the oxide film.

A bonding method has: an oxide film forming step S10 on an irradiated surface 62a1 to form an oxide film OM having a film thickness corresponding to a first output W1 and an irradiation time of a laser beam L1 forming the oxide film; a step S12 for detecting a first reflected laser beam to detect a second output W2; a first absorptivity calculation step S14 of calculating a first absorptivity for the laser film L1 forming the oxide film; Laser beam switching steps S16A and S16B, the laser beam forming the oxide film, on the irradiated surface 62a1 is emitted to switch to a Warmbondlaserstrahl; and a hot bonding step S3, a first bonding surface 62b to heat until the temperature thereof reaches a predetermined bonding temperature Ta, and the first bonding surface 62b to a second bonding surface 51a to bond.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• JP 4894528 [0002, 0002, 0002, 0004]
• JP 5602050 [0002, 0002, 0002, 0004]
• JP 2014-228478 A [0002, 0003, 0003, 0004, 0005, 0005, 0006]

Claims (12)

 A bonding method of bonding a first bonding surface of a first metal member to a second bonding surface of a second metal member in contact with the first bonding surface by irradiating a hot bonding laser beam on an irradiated surface of the first metal member to heat the first bonding surface, the bonding method comprising: an oxide film forming step of radiating a laser beam forming an oxide film with a first output to the irradiated surface of the first metal member and forming on the irradiated surface an oxide film having a film thickness corresponding to the first output and an irradiation time of the laser beam forming the oxide film; a step of detecting a first reflected laser beam to detect a second output which is a output of a first reflected laser beam generated from the laser film forming the oxide film due to being reflected by the irradiated surface; a first absorptivity calculating step, a first absorbing ability of the irradiated surface of the first metal element for the oxide film forming laser beam from the first output of the oxide film forming laser beam emitted in the oxide film forming step and the second output of the first reflected laser beam; which was detected in the step of detecting the first reflected laser beam; a laser beam switching step of switching the oxide film forming laser beam irradiated on the irradiated surface to the hot bond laser beam if it is determined that the first absorbing ability is equal to or higher than a predetermined absorbing ability; and a hot bonding step of, after switching to the hot bond laser beam, radiating the hot bond laser beam onto the irradiated surface with a third output to heat the first bonding surface until a temperature of the first bonding surface reaches a predetermined bonding temperature and bonding the first bonding surface to the second bonding surface.  A bonding method according to claim 1, wherein the predetermined bonding temperature is a temperature at which the first bonding surface and the second bonding surface are set in a solid phase state that occurs at a temperature lower than a liquid-phase temperature and allows bonding therebetween in a solid state, and in the hot bonding step, the first bonding surface and the second bonding surface in the solid phase state are pressed against each other in a press bonding direction to be bonded together.  The bonding method according to claim 1 or 2, wherein, in the warm bonding step, the third output of the warm bond laser beam is lower than the first output of the laser film forming the oxide film.  A bonding method according to any one of claims 1 to 3, wherein in a ratio with the film thickness of the oxide film, the first absorbing ability has a periodicity in which its local maximum value and local minimum value appear alternately with a change in film thickness in a rising direction, and also has a property in which the first absorbing ability is minimal when the film thickness of the oxide film is zero, the predetermined absorbance in the laser beam switching step having the periodicity in proportion to the film thickness is set within a range of the first absorbance corresponding to a film thickness range which is a combination of a first film thickness range and a second film thickness range; the first film thickness region is a film thickness region in which the film thickness of the oxide film exceeds zero and is smaller than a first local minimum film thickness corresponding to a first local minimum value corresponding to a local minimum value of the first absorptivity between a first local maximum film thickness a first local maximum value, which appears as a local maximum value of the first absorption capacity for the first time, and a second local maximum film thickness corresponding to a second local maximum value, which is the local maximum value of the first absorption capacity following the first local maximum value appears, appears, and the second film thickness range is a film thickness range in which the film thickness is equal to or greater than the first local minimum film thickness, the second local maximum film thickness is included, and the film thickness is smaller than a second local minimum film thickness corresponding to a second local minimum thickness. Is value which appears as the local minimum value of the first absorbency between the second local maximum film thickness and a third local maximum film thickness corresponding to a third local maximum value subsequent to the second maximum value of the first absorbency local maximum value appears.  The bonding method according to claim 4, wherein the range of the first absorption ability ranges from 20% to 60%. A bonding method according to claim 4 or 5, wherein the predetermined absorbance in the laser beam switching step which is the periodicity in Ratio with the film thickness is set within the range of the first absorbing ability corresponding to the first film thickness range.  A bonding method according to any one of claims 4 to 6, wherein the predetermined absorbability is set to the first local maximum value.  A bonding method according to any one of claims 4 to 6, wherein the predetermined absorbency is set to 40%.  The bonding method according to any one of claims 1 to 8, wherein at the oxide film forming step, the laser beam forming the oxide film is incident perpendicularly to the irradiated surface.  A bonding method according to any one of claims 1 to 9, further comprising: in the hot bonding step, a second reflected laser beam detection step detects a fourth output that is a second reflected laser beam output that is reflected from the warm bond laser beam irradiated on the irradiated surface with the third output due to reflection irradiated surface is generated, and a second absorptivity calculating step of calculating a second absorptivity of the irradiated surface of the first metal member for the hot bond laser beam from the third output and the fourth output; in which in the warm bonding step the third output is set based on the second absorptivity which changes with the increase of an irradiation time of the hot bond laser beam.  A bonding apparatus that radiates a hot bond laser beam to an irradiated surface of a first metal element to heat a first bonding surface of the first metal element, and bonds the first bonding surface to a second bonding surface of a second metal element in contact with the first bonding surface, wherein the bonding device comprises : a laser beam matching radiation unit that controls to irradiate, with a first output, a laser beam forming an oxide film on the irradiated surface of the first metal member to form on the irradiated surface an oxide film having a film thickness corresponding to the first output and an irradiation time of the oxide film Laser beam has; a first reflected laser beam detecting unit that detects a second output that is a output of a first reflected laser beam generated from the laser film forming the oxide film due to being reflected by the irradiated surface; a first absorptivity calculating unit that calculates a first absorptivity of the irradiated surface of the first metal element for the oxide film forming laser beam from the first output and the second output; a laser beam switching unit that switches the laser film forming the oxide film irradiated on the irradiated surface to the warm bond laser beam if it is determined that the first absorptivity is equal to or higher than a predetermined absorbance; and a hotbonding control which, after switching to the hotbond laser beam, performs a control to radiate the hotbond laser beam onto the irradiated surface with a third output to heat the first bonding surface until a temperature of the first bonding surface reaches a predetermined bonding temperature, and the first bonding surface to bond to the second bond surface.  The bonding apparatus according to claim 11, wherein the first reflected laser beam detection unit detects the second output of the first reflected laser beam with a power meter.

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